Require HTTPS for external links

[Jim8y]

Summary

• parse external command URLs before opening them
• only allow absolute HTTPS URLs through OpenUrl and LaunchUrl
• show the existing generic error toast for invalid or unsafe URL values

Verification

• confirmed origin/master passes raw strings directly to Browser.OpenAsync / Launcher.TryOpenAsync
• confirmed this branch gates both command paths through TryCreateWebUri and Uri.UriSchemeHttps
• git diff --check
• dotnet build OneGateApp/OneGateApp.csproj -f net10.0-android -c Debug -v:minimal /p:UseSharedCompilation=false /p:RuntimeIdentifier=android-x64

[Jim8y]

iOS verification update 2026-04-30:

• Attempted dotnet build OneGateApp/OneGateApp.csproj -f net10.0-ios -c Debug -v:minimal /p:UseSharedCompilation=false /p:RuntimeIdentifier=iossimulator-arm64 on this PR branch.
• Result: blocked by local iOS toolchain, not by a PR-specific compiler error.
• Error: installed .NET iOS SDK 26.2.10233 requires Xcode 26.3, but this machine currently has Xcode 16.2.
• Simulator status: simctl list runtimes and simctl list devices are empty, so there is no available iOS simulator runtime/device to run.
• Next requirement: install matching Xcode 26.3 plus iOS simulator runtime, or switch project/workload to versions compatible with Xcode 16.2, then rerun iOS build/run smoke.

Branch checked: codex/require-https-external-links
Raw result file: /tmp/onegate-ios-pr-validation-20260430-072110.tsv

[Jim8y]

iOS local validation updated after fixing the local simulator/toolchain environment.

Supersedes my earlier local iOS validation failure note. Root cause was local environment mismatch, not this PR:

• Xcode was upgraded to 26.4.1.
• iOS 26.4.1 Simulator runtime was installed and booted.
• Simulator dyld cache initialization completed.
• Build uses simulator ad-hoc signing to avoid requiring a personal Apple Development cert locally.

Validated locally:

dotnet build OneGateApp/OneGateApp.csproj \
  -f net10.0-ios \
  -c Debug \
  -v:minimal \
  /p:UseSharedCompilation=false \
  /p:RuntimeIdentifier=iossimulator-arm64 \
  /p:ValidateXcodeVersion=false \
  /p:CodesignKey=- \
  /p:CodesignProvision= \
  /p:ProvisioningType=automatic

Result: PASS for PR #23. Log: /tmp/onegate-ios-pr-logs/pr-23.log on my local machine.